1. Field of the Invention
The present invention relates in general to telecommunications systems and, more particularly, to a method for allocating a mobile station Temporary Mobile Subscriber Identification (TMSI) number to provide telecommunication services to a particular user group classification.
2. Description of the Related Art
With the increasing popularity of wireless telecommunications systems (e.g., wireless cellular telecommunications systems), telecommunication service providers offer many different types of telecommunication services to their respective customers. Such services are generally provided to users on a subscription basis and, therefore, such users are generally referred to as "subscribers."
To facilitate such services, it is desirable for providers of wireless telecommunications networks to classify mobile stations (e.g., vehicular and portable, hand held cellular telephones and other communication devices) belonging to specific subscribers as an identifiable group for various services, such as sending one page to all members belonging to a specified group classification. In order to do so, it is necessary for the service provider to be able to identify the user associated with a particular mobile station regardless of where that mobile station is within the network and to ascertain whether that particular user subscribes to a specific group classification.
In conventional cellular networks, each mobile station has a unique Mobile Identification Number (MIN) or International Mobile Subscriber Identification number (IMSI) for identification purposes used in billing, record keeping and the like. However, when a mobile station moves outside of its home location served by a Mobile Switching Center (MSC) and enters a visitor location served by another MSC, the mobile station is assigned a Temporary Mobile Subscriber Identification (TMSI) number for identification purposes similar to the MIN or IMSI in network use. A conventional method for generating a TMSI is described, for instance, in U.S. Pat. No. 5,375,251 to Pfundstein. In conventional wireless telecommunications systems, the TMSI number is a unique, often randomly assigned, identification number that is typically 20-24 bits in length. In conventional systems, therefore, the TMSI number is not allocated to more than one user of a given system served by that MSC at one time. Consequently, the TMSI number is usually invalidated when the mobile station crosses into a new location served by a different MSC or after a predetermined period of time following initial allocation of the TMSI number (e.g., 12 hours).
Accordingly, because mobile stations frequently change location within the wireless network and are often controlled by different MSC's, it is problematic for conventional wireless telecommunications systems to effectively identify the user associated with a particular mobile station when the mobile station is outside its home location in order to ascertain whether that particular user subscribes to a specific group classification. In a conventional wireless network, therefore, to page all mobile stations belonging to a particular group of subscribers to answer a call in parallel, it is presently necessary for the calling party to send a separate page to the mobile station corresponding to each member of the group. This procedure, however, has proven to be inconvenient and does not provide sufficient flexibility to take into account the change in locations of mobile stations within the wireless network.
As an alternative to sending a separate page to the mobile station corresponding to each member of the group, a group identification could be preprogrammed into a mobile station to identify the user of that mobile station as a member of a particular group. However, this procedure does not allow the group membership to be dynamically assigned (e.g., as a function of location, time of day, day of week, etc.).